Field of the Invention
The invention relates to a bone anchoring device which includes a bone anchoring element for anchoring in a bone or a vertebra and a receiving part for coupling the bone anchoring element to a stabilization element such as a spinal rod, where the bone anchoring element is pivotable in the receiving part and can be pivoted to at least one side with an enlarged pivot angle.
Description of Related Art
A bone anchoring device of this type is described in U.S. Pat. No. 6,736,820. The bone anchoring device includes a bone screw and a receiving part with an open first bore and a substantially U-shaped cross-section for receiving the rod and a second bore on the end opposite to the first bore and a seat for the head. In order that the screw member can be pivoted to at least one side by an enlarged angle, the edge bounding the free end of the second bore is of asymmetric construction. In a modified embodiment an insert piece is provided, which has a spherical bottom as the seat for the head. This allows to change the orientation of the enlarged pivot angle.
US 2005/0154391 A1 describes a bone anchor assembly with a bone anchor and a receiving member. The receiving member has a first section having a first bore defining a first bore axis and a second section having a second bore defining a second bore axis and being sized to receive at least a portion of the bone anchor, wherein the second bore axis intersects the first bore axis. The second section is rotatable about the first bore axis. In an embodiment, the second section is seated internally within the first section.
Since the second section is rotatable with respect to the first section, it is possible to pivot bone anchors out of alignment with one another to avoid interference due to the close proximity of adjacent vertebrae.
Another polyaxial bone anchor is described in US 2007/0118123 A1, wherein a locking element is provided, which is shaped and configured to allow an anchoring member such as a screw or a hook to polyaxially rotate at large angles about a central axis of the bone anchor before compression locking the anchoring member within an anchor head.